1. Field of the Invention
The present invention relates to a reciprocating vibrator used in a mobile phone etc., more particularly relates to a structure of a reciprocating vibrator having a weight reciprocating in a thrust direction.
2. Description of the Related Art
As shown in FIG. 7, a vibration linear actuator 1 disclosed in Japanese Patent Publication (A) No. 2003-154314 is provided with a ring-shaped outer yoke 4 as a weight having a permanent magnet 5 at its inner circumference side, a first plate spring 7 fastened to a first end face 4a of this outer yoke 4 by elastic deformation of an outer circumference side tail part 7a, a second plate spring 6 the same as this first plate spring 7 fastened to a second end face 4b of the outer yoke 4 by elastic deformation of an outer circumference side tail part 6a, and a stator having a coil 2 supporting the first and second plate springs 7, 6 and generating a reciprocating vibrating magnetic field with respect to the outer yoke 4 at an inner circumference side of the permanent magnet 5. The stator is further provided with a plastic base 9 having at its bottom surface power feed lands 11 and having a shaft 8 sticking out from it and an inner yoke 3 on this base 9 having the shaft 8 at its center and also forming a coil bobbin of the coil 2. The inner circumference side 7b of the first plate spring 7 is fit with a first projection 3a of the inner yoke 3, while the inner circumference side 6b of the second plate spring 6 its fit with a second projection 3b of the inner yoke 3 whereby they are clamped between the base 9 and the inner yoke 3.
In the state not feeding power to the coil 2, the outer yoke 4 serving as the weight stops at the illustrated axial direction neutral position where the elastic springback force acting outward to the first end face 4a side due to the first plate spring 7 and the elastic springback force acting outward to the second end face 4b side due to the second plate spring 6 balance, but when the coil 2 is supplied with an alternating current and a reciprocating vibrating magnetic field is formed, the first plate spring 7 and the second plate spring 6 alternately repeat an operation of springing back to a free state of the planar shape, so the outer yoke 4 reciprocates in the thrust direction and generates reciprocating vibration.
Patent Literature 1: Japanese Patent Publication (A) No. 2003-154314 (FIG. 1)
In the above vibration linear actuator 1, the inner yoke 3 is fastened to the shaft 8 by welding etc. and the shaft 8 may be press-fit into a hole of a thick plastic base 9 to make it stand up, so originally the shaft 8 is poor in reliability of fastening. Further, at the top and bottom dead points of the reciprocating vibration of the outer yoke 4, impact like detaching force acts on the shaft 8. For this reason, a metal outer cover (case) 12 is used to cover the inner yoke 3 and outer yoke 4 and is fastened by swaging at the cover swaged parts 12a provided at the base 9. The outer cover 12 also has the role of holding down the shaft 8 and inner yoke 3 from above, but this invites an increase in the number of parts by the amount of the outer cover 12.